Balloon-in-basket ablation catheter

ABSTRACT

A catheter comprises an expandable spline structure defining a distal tip portion of the catheter. The spline structure comprises a plurality of individual splines, and each spline is configured to support a plurality of energy transfer elements and/or temperature sensors. An expandable balloon configured to be associated with the spline structure is unattached to the spline structure along its length.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Stage Entry of International applicationno. PCT/US2018/036140, filed 5 Jun. 2018 (the '140 application), andpublished under International publication no. WO 2018/226751 on 13 Dec.2018. This application claims priority to Provisional patent applicationNo. 62/515,500, filed 5 Jun. 2017 (the '500 application). The '140application and the '500 application are all hereby incorporated byreference as though fully set forth herein.

BACKGROUND a. Field

This disclosure relates to a combination balloon-basket catheter forelectrical mapping and tissue ablation.

b. Background Art

Electrophysiology (EP) catheters are used in a variety of diagnosticand/or therapeutic medical procedures to correct conditions such asatrial arrhythmia, including for example, ectopic atrial tachycardia,atrial fibrillation, and atrial flutter. Arrhythmia can create a varietyof dangerous conditions including irregular heart rates, loss ofsynchronous atrioventricular contractions and stasis of blood flow whichcan lead to a variety of ailments and even death.

Typically in a procedure, a catheter is manipulated through a patient'svasculature to, for example, a patient's heart, and carries one or moreelectrodes which may be used for mapping, ablation, diagnosis, or othertreatments. Once at the intended site, treatment may include radiofrequency (RF) ablation, cryoablation, lasers, chemicals, high-intensityfocused ultrasound, etc. An ablation catheter imparts such ablativeenergy to cardiac tissue to create a lesion in the cardiac tissue. Thislesion disrupts undesirable electrical pathways and thereby limits orprevents stray electrical signals that lead to arrhythmias. As readilyapparent, such treatment requires precise control of the catheter duringmanipulation to and at the treatment site, which can invariably be afunction of a user's skill level.

Prior practice for delivering multiple ablations to tissue involvesmaking a first ablation at a single point with an ablation catheter,then moving the ablation catheter on to the second ablation at a secondpoint, and then moving to ablation catheter to the third site and so on.The single point ablations are made, often adjacent to one another,creating a lesion line. A frequent location for ablation lines arearound/between the pulmonary veins in the left atrium of the heart.There are devices in development or being commercialized that attempt toachieve a sufficient block of ablations with minimal applications ofenergy. These are typically referred to as “one-shot-PVI” (pulmonaryvein isolation) devices. Existing designs include diagnostic catheterswith a hoop and balloon mounted designs with features to apply energy.Existing designs are challenged when it comes to maintaining consistentcontact between the tissue/vessel and all of the electrodes.

BRIEF SUMMARY

In an embodiment, a catheter comprises an expandable spline structuredefining a distal tip portion of the catheter, the spline structurecomprising a plurality of individual splines, each spline configured tosupport a plurality of energy transfer elements; and an expandableballoon configured to be positioned inside the spline structure; whereinthe balloon and the spline structure are unattached along a length ofthe spline structure.

In another embodiment, a catheter comprises an expandable splinestructure defining a distal tip portion of the catheter, the splinestructure comprising a plurality of individual splines, each splineconfigured to support a flexible circuit including at least one of anenergy transfer element and a temperature sensor; and an expandableballoon configured to be positioned inside the spline structure.

In another embodiment, a catheter comprises an expandable splinestructure defining a distal tip portion of the catheter, the splinestructure comprising a plurality of individual splines, each splineconfigured to support a plurality of energy transfer elements; and anexpandable first balloon configured to be positioned inside the splinestructure; wherein the first balloon is uninflated upon entry into thespline structure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view depicting an embodiment of a catheter inaccordance with the present disclosure.

FIG. 2 is a schematic view of an embodiment of a balloon-in-basketdevice in accordance with the present disclosure.

FIG. 3 is a schematic view of an embodiment of a balloon-in-basketdevice in accordance with the present disclosure.

FIG. 4 is a schematic view of an embodiment of a balloon-in-basketdevice in accordance with the present disclosure.

FIG. 5A is a schematic view of an embodiment associated with potentialaxial blood leakage.

FIG. 5B is a schematic view depicting solutions to the potential axialblood leakage illustrated in FIG. 5A, in accordance with the presentdisclosure.

FIG. 6 is a schematic view of another embodiment of a balloon-in-basketdevice in accordance with the present disclosure.

FIG. 7 is a schematic view of another embodiment of a balloon-in-basketdevice in accordance with the present disclosure.

FIG. 8A is a schematic perspective and side view of a single-basketspline subassembly in accordance with the present disclosure.

FIG. 8B is a schematic perspective view of a single-basket splinesubassembly in accordance with the present disclosure.

FIG. 8C is a schematic view of two adjacent splines in accordance withthe present disclosure.

FIG. 8D is an isometric cross-sectional view through line Z-Z of FIG.8C, in accordance with the present disclosure.

FIG. 8E is a schematic view of four splines in accordance with thepresent disclosure.

FIG. 9A is a schematic view of an embodiment of a balloon for use with aspline structure in accordance with the present disclosure.

FIG. 9B is a cross-sectional view through line 9B-9B of FIG. 9A, inaccordance with the present disclosure.

FIG. 9C is a schematic view of an embodiment of a balloon for use with aspline structure in accordance with the present disclosure.

FIG. 9D is a cross-sectional view through line 9D-9D of FIG. 9C, inaccordance with the present disclosure.

FIGS. 10A-D are schematic views depicting embodiments in which a balloondoes not inflate associated splines, in accordance with the presentdisclosure.

DETAILED DESCRIPTION

FIG. 1 is a schematic view depicting a catheter 12 for use in apatient's body 14 and connected to an energy/fluid supply 16 (e.g., aradiofrequency (RF) ablation generator, a coolant supply) according tothe present disclosure. In an embodiment, the catheter 12 may be anablation catheter. The catheter 12 can be configured to be inserted intothe patient's heart 18. The catheter 12 may include a handle 20 and ashaft 22 having a proximal end portion 24, a distal end portion 26, anda tip portion 28 disposed at the distal end portion 26 of the shaft 22.The catheter 12 may further include other conventional components suchas, for example and without limitation, a temperature sensor, a positionsensor, additional sensors or electrodes, and corresponding conductorsor leads.

The shaft 22 can be an elongate, tubular, flexible member configured formovement within the body 14. The tip portion 28 of the shaft 22supports, for example and without limitation, sensors and/or electrodesmounted thereon. The tip portion 28 may include ablation elements (e.g.,ablation tip electrodes for delivering RF ablative energy). The shaft 22may also permit transport, delivery, and/or removal of fluids (includingirrigation fluids, cryogenic ablation fluids, and bodily fluids),medicines, and/or surgical tools or instruments.

FIG. 2 is a schematic view of a balloon-in-basket device 100 forming thedistal tip portion of an ablation catheter, such as the catheter 12described above with respect to FIG. 1 . The illustrated embodimentincludes a delivery lumen (or port) 102, a spline structure 103supporting multiple energy transfer elements 104, and an interiorinflatable ablating balloon 105. The balloon 105 is deflated and thebasket splines 103 are collapsed such that the device 100 is deliverablethrough a bodily lumen to an ablation site.

The energy transfer elements 104 can include, for example, but notlimited to, electrodes, flexible electrodes, ultrasound transducers,lasers, chemical ablation sources, cryoablation sources, and/or heatablation sources. The energy transfer elements 104 can also includeablation elements, such as those described in commonly owned U.S.Provisional Patent Application No. 62/515,501 which is herebyincorporated by reference in its entirety as though fully set forthherein.

The spline structure 103 can be made from a material that retains itsshape and permits self-expansion after being collapsed, such as nitinolor other materials that have shape memory or superelasticity. The energytransfer elements 104 situated along the spline structure 103 can beflexible electrodes used to characterize and map tissue that they comeinto contact with at a treatment site. In an embodiment, the treatmentsite can be the tissue forming and surrounding the pulmonary veins, afrequent origination site for the abnormal electrical activity thatresults in atrial fibrillation. In other embodiments, the treatment sitecan be renal artery tissue or a bodily ostium, lumen, or sphincter.Following delivery to the treatment site, such as through delivery lumen102, the spline structure 103 can mechanically expand such that theenergy transfer elements 104 preferably abut potential pulmonary veintarget tissue. This expansion of the spline structure 103 isschematically illustrated in FIG. 3 .

In addition, the balloon 105 can expand, such as when cryogenic fluid orheated fluid (e.g., saline) is delivered to the internal chamber of theballoon 105 via delivery lumen 102. The expanded balloon 105, shownschematically in FIG. 4 , can allow for cryogenic or thermal ablation oftarget tissue abutting the pulmonary veins.

It should be noted that the balloon 105 and the spline structure 103 canbe structurally separate, as illustrated in FIGS. 2-4 . In other words,the balloon 105 and the spline structure 103 are not bonded, laminated,integrated, or otherwise attached to each other. This structuralseparation allows the balloon 105 and the spline structure 103 to beseparately expandable/collapsible, as well as separately introducible.

Several embodiments of the combined spline structure 103 and balloon 105exist in accordance with the present invention. For example, the splinestructure 103 can mechanically engage tissue (e.g., pulmonary veintissue) and support energy transfer elements 104 (e.g., ablating RFelectrodes) while the balloon 105 is separately inflated against thetissue and spline structure 103, as in FIG. 4 . Cryogenic or heatedfluid can flow through the inflated balloon 105. The energy transferelements 104 can also be used for mapping or pacing cardiac tissue.

In another example, the energy transfer elements 104 can be used foronly mapping or pacing, and not for ablation. In this case, the inflatedballoon 105 can ablate tissue using cryogenic fluid or hot saline, forexample.

In another example, the inflated balloon 105 can serve the purpose ofcausing the spline structure 103 to directly abut the target tissue,such that the spline energy transfer elements 104 can perform RFablation on the tissue. The inflated balloon 105 may allow the splinesto attain a more favorable shape for close tissue contact than would bepossible via mechanical actuation of the spline structure alone (i.e.,without the balloon 105). In this example, the energy transfer elements104 may also map or pace tissue.

In another example, the energy transfer elements 104 on the splinestructure 103 can perform ablation (regardless of how they are actuatedagainst the tissue), and the inflated balloon 5 can serve the primarypurpose of inhibiting blood flow from the pulmonary veins into thespline structure 103.

FIG. 5A schematically illustrates an embodiment associated withpotential axial blood leakage. When the spline structure 103 and theballoon 105 are in their expanded state abutting target tissue 106,blood can leak along the spline structure 103 into a triangular openchannel area 110 defined by the target tissue 106, the balloon 105, anda flexible electrode 109C (or another energy transfer element asdescribed above) sitting on top of a flexible circuit 109B, which inturn sits on top of a metal spline core 109A of the spline structure103. The blood leakage into the open channel area 110 can reduce thethermal effect (whether cooling or heating) of ablation.

FIG. 5B is a schematic view depicting solutions to the axial bloodleakage illustrated in FIG. 5A. FIG. 5B shows a spline structure 103 a(including a metal spline core 109A_(i), a flexible circuit 109B_(i),and a flexible electrode 109C_(i)) with a modified cross-sectional shapethat leaves a reduced open channel area 110 a into which blood can leak.The spline structure 103 a can be further modified to include an addedmaterial, such as elastomeric silicone or urethane (not shown), whichcan be placed in or near the reduced open channel area 110 a in order tocreate a better blood-sealing fit.

Alternatively or additionally, a gel or compliant coating (not shown)can be employed on the surface of the balloon 105 or spline structure103 to afford such a seal against blood leakage. The gel or compliantcoating can be configured to withstand hot or cold ablationtemperatures, to be resistant to shedding, and to be compatible withblood. The gel or compliant coating could be applied to the balloon 105or the spline structure 103 during manufacturing, or it could be appliedby a user. Alternatively, the balloon 105 could extrude the gel orcompliant coating out of small holes in the balloon wall (not shown) inorder to fill gaps between the balloon 105 and the tissue 106.

FIG. 6 is a schematic illustration of another embodiment of aballoon-in-basket device 100A with the spline structure 103 mechanicallyexpanded to about 75% of maximum expansion. In this embodiment, theballoon 105, shown here in its uninflated state, is mounted on acatheter, wire, or shaft 112 that has been inserted through a workingport in lumen 102. The uninflated balloon 105 can be pushed forward asindicated by arrow 114 to assume position 115 where it can then beinflated. Thus, the device 100A can be used can be used in anon-obstructing manner (i.e., when the balloon 105 is not inflated,fluid can flow around it) or in an obstructing manner (i.e., when theballoon 105 is inflated).

In an another embodiment, the balloon 105 can be preassembled in thespline structure 103 and an inflating lumen 113 for the balloon 105 canbe later inserted and flow-coupled in-situ to the balloon 105. Theadvantage of such an embodiment is that the balloon 105 can be larger orthicker-walled than it would otherwise need to be in order to fitthrough a working port.

FIG. 7 schematically depicts another embodiment a balloon-in-basketdevice 100B in which there is more than one balloon. Double balloonshave been used to prevent cryocoolant from leaking into blood upon thefailure of one of the balloons. The two balloons, 105A and 105B, shownin FIG. 7 are not coinflated. The outer balloon 105A is inflated toanchor the spline structure 103. The inner balloon 105B is inflatedagainst the tissue and already deployed outer balloon 105A to performthermal ablation (either cooling or heating). The outer balloon 105A notonly acts as a backup in case of failure of the inner balloon 105B, butit also functions as an independent fixation means for the splinestructure 103. The outer balloon 105A can be inflated, if desired, by anon-coolant gas or liquid, such as carbon dioxide or saline. The innerballoon 105B is shown as being inserted into the interior of the splinestructure 103 in the direction of arrow 114′ to position 115′ beforeinflation. A working port arrangement is not necessarily required forthis embodiment, as the two balloons, 105A and 105B, and the splinestructure 103 can all be part of the same device 100B. Aftercryoablation or hot fluid ablation, the gas or liquid in inner balloon105B can be deflated while the outer balloon 105A remains inflated tofixate the spline structure 103 in a way that prevents tissue cooling.

FIG. 8A depicts schematic perspective and side views of a single-basketspline subassembly 109A/B/C shown bent at a radius R. The radius R maybe variable. The spline subassembly 109A/B/C comprises a metallic splinecore 109A, a core-supported flexible circuit 109B, and supportedelectrodes 109C. An electrically- and thermally-insulative over coating111A (e.g., a conformal, dipped, or over-molded coating), is situatedonly in the non-ablating regions L₁ and L₃. Ablating region L₂ comprisesthe exposed spline core 109A and flexible electrode circuit 109B/C.Thus, in region L₂, heat can flow out of the tissue 106 across the thinflexible electrode circuit 109B/C and across the nitinol or othermetallic spline core 109A. On the other hand, regions L₁ and L₃ arethermally insulated from blood and tissue by coating 111A. Thus, anyheat which leaves tissue and tries to cross the spline subassembly109A/B/C along thermally insulated regions L₁ and L₃ will be blocked.This arrangement creates a thermal compromise wherein the splinesubassembly 109A/B/C allows thru-flow of heat where needed (i.e., in theablating region L₂) and discourages heat from being extracted fromnon-ablating regions L₁ and L₃. An advantage of the design of thisspline subassembly 109A/B/C is that a wide spline core 109A and a wideflexible electrode circuit 109B/C can be used, as localized heat flowingthrough the ablating spline region L₂ prevents a thermally untreatedregion from forming beneath the wide spline.

FIG. 8B is a schematic view of another embodiment of a single-basketspline subassembly 109A′/109B′/109C′. In this embodiment, the metallicspline core 109A′ can be a round nitinol core. Similar to the embodimentshown in FIG. 8A, a thermally- and electrically-insulating material 111Acoats the spline subassembly 109A′/109B′/109C′ in regions L₁ and L₃.This arrangement creates a thermal compromise in which a lesion isformed underneath the spline in region L₂, but not in regions L₁ and L₃.The flexible circuit 109B′ can comprise a circumferentially wrappedflexible circuit (not shown), a longitudinally bonded flexible circuit(as shown in FIG. 8B), or insulated wires wrapped around the spline core109A′ (not shown) and laser exposed at electrode sites 109C′.

It should be noted that the embodiments described above with respect toFIGS. 8A and 8B can be combined. For example, the spline core 109A/109A′can be rectangular in region L₂ and round in regions L₁ and L₃, or viceversa. It should further be noted that one or more of a thermocouple,thermistor or other temperature sensor in any of the sections L_(1,2,3)and facing either toward tissue or toward the juxtaposed balloon, forexample.

FIG. 8C is a schematic depiction of an embodiment of two adjacentsplines 109A″. The splines 109A″ can be nitinol splines with a width W₁.Laminated to the splines 109A″ are individual flexible circuits 109B″.The flexible circuits 109B″ are overhanging the physical edges of thesplines 109A″ in a region with a width W₂ that is wider than W₁. Thesplines can be rectangular, as shown, or round (as in FIG. 7 b ). Theoverhanging flexible circuits 109B″ can be bonded (as shown) to thenitinol (or other spline material) splines 109A″. Alternatively, theflexible circuits 9B″ can be otherwise mechanically connected to thesplines 109A″, such as by surrounding them (not shown). In addition, theoverhanging flexible circuits 109B″ may overhang on one or both sides ofeach spline 109A″. An advantage of a single-side overhang is that whenthe splines 109A″ are collapsed they can more easily compress togetheralong with their flexible circuits 109B″. The overhanging flexiblecircuits 109B″ are depicted as supporting electrodes 109C″ as well asthermocouples 109D.

FIG. 8D is an isometric cross-sectional view through line Z-Z of FIG. 8Cshowing the overhanging flexible circuit 109B″ and spline 109A″. Phantomlines 112A and 112B show that the overhanging flexible circuit 109B″ canbe pre-formed and have a radius (not shown). The radius can make iteasier for the splines 109A″ and flexible circuits 109B″ to close afterbeing opened. Further, compression caused by a balloon, such as balloon105 in FIGS. 2-6 , could force the overhanging flexible circuits 109B″to be flattened or to conform against tissue and the inflated balloonsurfaces.

Returning to FIG. 8C, the overhanging flexible circuits 109B″ aredepicted as laminated to the interior surfaces of the splines 109A″ thatface the backing balloon (not shown). Note, however, that the electrodes109C″ face the tissue 106 (shown in FIGS. SA-C). Alternatively, theoverhanging flexible circuits 109B″ may be mounted on the exteriorsurfaces of the splines 109A″ facing the tissue (not shown). In eithercase, the electrodes 109C″ will face tissue and the thermocouples 109Dmay face tissue, the balloon, or a tissue/balloon interface. Thethermocouples 109D may also be mounted in thru-holes in the overhangingflexible circuits 109B″. Thus, by using flexible circuits, theelectrical contact can be routed (during manufacture) to either flexiblesurface regardless of which surface faces the splines.

An advantage of having thermocouples 109D in the overhanging flexiblecircuits 109B″ is that they can provide an accurate balloon/tissueinterface temperature without being skewed by the thermal conductivityof an underlying or overlying heat-sinking spline. Another advantage ofthe overhanging flexible circuits 109B″ is that the size of electrodes109C″ can be much larger than if they were laterally constrained to thespline width W₁ (as opposed to the wider W₂ dimension). The width W₂ ofthe overhanging flexible circuit portions 109B″, shown in section Z-Z ofFIG. 8D as potentially being pre-curved and balloon-flattened, mightco-integrate a spring element or layer (not shown) to provide thisspringiness and positive radius in the proper direction of phantom lines112A or 112B as selected during design. A third potential advantage ofthe overhanging flexible circuits 109B″ is that they may allow for theuse of fewer splines—such as three or four splines rather than five orsix splines—at least in the case wherein the flexible circuits 109B″overhang splines 109A″ on both sides. Using fewer splines allows moreroom for other elements.

FIG. 8C also shows, in phantom, a bridging flexible portion 113Aconnecting two overhanging flexible circuits 109B″. At least part of thebridging flexible portion 113A may be pressed against tissue by theballoon 105 (see FIGS. 2-6 ). A bridging flexible electrode (and/orthermocouple) 113B, depicted in phantom, can be located on the bridgingflexible portion 113A. Bridging flexible electrodes (and/orthermocouples) 113B can be present in addition to or instead of thespline-mounted electrodes 109C″ or thermocouples 109D. Such bridgedflexible circuitry can allow for fewer splines.

In an embodiment, a higher pressure balloon can be used to attain betterthermal contact with tissue without mechanically overloading the ostiumof the pulmonary vein. The higher pressure balloon may also allow forsuperior cryofreezing parameters, such as a faster cooling rate or moreelastic deformation of the balloon into an asymmetrical ostium,particularly if the ostium is mechanically supported by splines. Thepresent inventors believe that overexpansion of the balloon is lesslikely in a multi-spline arrangement because more elastic balloondeformation may be allowed than for a symmetric balloon with no splines.In other words, a more flexible balloon can bulge outward betweensplines without escaping from the spline structure.

A potential advantage to above-described embodiments, in which thesplines 109A″/overhanging flexible circuits 109B″ are not bondeddirectly to the balloon 105 (see FIGS. 2-6 ), is that the balloon 105and overhanging flexible circuits 109B″ may be less stressed and morereliable.

FIG. 8E is a schematic view showing four splines—109A1, 109A2, 109A3,and 109A4. Although four splines are shown here, any number of splinesmay be used. No flexible circuits, electrodes, or thermocouples areshown here for purposes of simplification. Each spline 109A1, 109A2,109A3, 109A4 can be individually adjustable by an amount ΔL, resultingin a radial position change of that specific spline by an amount ΔR. Theshape of the splines 109A1, 109A2, 109A3, 109A4 can be adjusted fromround to oval to better seat electrodes and thermocouples in anoval-shaped pulmonary vein, such as at the superior left region of theof the heart. A mechanical mechanism, such as an axial sliding wire(s),can push or pull some or all of the splines 109A1, 109A2, 109A3, 109A4in order to adjust their shape.

FIGS. 9A-9D are schematic views of various balloon embodiments that canbe used in accordance with the present disclosure. In FIG. 9A, asymmetrical balloon 105C is depicted at a distal end of a delivery lumen102′. As shown in FIG. 9B, the symmetrical balloon 105C has a diameter Dand thickness t. In FIG. 9C, an asymmetrical balloon 105D is depicted ata distal end of a delivery lumen 102″. As further shown in FIG. 9D, theasymmetrical balloon 105D has an elliptical or oval section defined bytwo radii, R₁ and R₂, which are separated by a distance d.

The asymmetrical balloon 105D may align with an asymmetric shape of apulmonary vein ostium, thereby facilitating entry and sealing of thecatheter balloon against tissue. The orientation or alignment of theballoon 105D can be determined in several ways. Radiographic markers(not shown) on the asymmetrical balloon 105D may be used in conjunctionwith fluoroscopy to indicate the orientation of the balloon 105D.Contrast injection may be used instead of or in addition to radiographicmarkers to determine the orientation of the balloon 105D. In addition,the splines 109A1, 109A2, 109A3, 109A4 shown in FIG. 8E may be employedin an asymmetrical shape and inserted into an asymmetrical pulmonaryvein ostium, after which the asymmetrical balloon 105D (or even thesymmetrical balloon 5C) can be inflated within the splines 109A1, 109A2,109A3, 109A4.

FIGS. 10A-10D are schematic views depicting another embodiment in whicha balloon 105E (e.g., a cryoballoon) does not inflate associated splines103′. In FIG. 10A, the balloon 105E contains a small EP basket comprisedof splines 103′ (which may comprise flexible circuits without a metalspline backer) and energy transfer elements 104′. This “standoff EPbasket” electrically operates through the walls of the balloon 105Ebefore, during, or after cryoablation. As shown in FIG. 10B, the splines103′ may be replaced by legs of a flexible circuit 103″, forming anaxial EP array of energy transfer elements 104″ proximal the cryoballoon105E. It may have its own activation balloon 105F, shown in phantom. Theenergy transfer elements 104″ of FIG. 10B can be particularly good atpicking up EP activity around the pulmonary vein ostium 115 around orunder the balloon 105F on surfaces sloped toward the EP array. Asdepicted in FIGS. 10A-10D, element 116 represents a wire hook retainer.

In FIG. 10C, an EP array (basket) has a radial looking axial part 103Aand a forward-looking annular part 103B. Again, the radial part can 103Adetect EP activity in the pulmonary vein lumen, whereas the annular part103B can detect EP activity on the pulmonary vein ostium face 115. InFIG. 10D, a combination side-looking radial portion 103A′ andforward-looking annular basket portion 103B′ is shown. The EP mappingstructures 103A′ and 103B′ can slide over the deflated balloon 105E,permitting both contact-free mapping (as shown, for example, in FIGS.10A and 10C) and contact-mapping.

It should be appreciated that the balloon dielectric constant,conductivity, and thickness may need to be optimized for signalintegrity according to the substance that fills the balloon (e.g.,balloon 105E or 105F in FIG. 10B) during mapping. The balloon may befilled with cryovapor, cryoliquid (cryomedix), saline, or a gas such asCO2.

It should also be appreciated that both a contact mapping array (asshown, for example, in FIGS. 6 and 7 ) and a non-contact mapping array(as shown, for example, in FIGS. 10A and 10C) can be combined in asingle device. While contact mapping arrays generally provide the mostaccuracy, non-contact mapping arrays have the advantage of not needingto be flattened against tissue (i.e., “standing off” the tissue). Thus,a device that combines both contact and non-contact mapping arrays canprovide advantages of each technique.

Although at least one embodiment of an apparatus and method for coolingtissue has been described above with a certain degree of particularity,those skilled in the art could make numerous alterations to thedisclosed embodiments without departing from the spirit or scope of thisdisclosure. All directional references (e.g., upper, lower, upward,downward, left, right, leftward, rightward, top, bottom, above, below,vertical, horizontal, clockwise, and counterclockwise) are only used foridentification purposes to aid the reader's understanding of the presentdisclosure, and do not create limitations, particularly as to theposition, orientation, or use of the disclosure. Joinder references(e.g., attached, coupled, connected, and the like) are to be construedbroadly and can include intermediate members between a connection ofelements and relative movement between elements. As such, joinderreferences do not necessarily infer that two elements are directlyconnected and in fixed relation to each other. It is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative only and not limiting.Changes in detail or structure can be made without departing from thespirit of the disclosure as defined in the appended claims.

Various embodiments are described herein to various apparatuses,systems, and/or methods. Numerous specific details are set forth toprovide a thorough understanding of the overall structure, function,manufacture, and use of the embodiments as described in thespecification and illustrated in the accompanying drawings. It will beunderstood by those skilled in the art, however, that the embodimentsmay be practiced without such specific details. In other instances,well-known operations, components, and elements have not been describedin detail so as not to obscure the embodiments described in thespecification. Those of ordinary skill in the art will understand thatthe embodiments described and illustrated herein are non-limitingexamples, and thus it can be appreciated that the specific structuraland functional details disclosed herein may be representative and do notnecessarily limit the scope of the embodiments, the scope of which isdefined solely by the appended claims.

Reference throughout the specification to “various embodiments,” “someembodiments,” “one embodiment,” or “an embodiment”, or the like, meansthat a particular feature, structure, or characteristic described inconnection with the embodiment is included in at least one embodiment.Thus, appearances of the phrases “in various embodiments,” “in someembodiments,” “in one embodiment,” or “in an embodiment”, or the like,in places throughout the specification are not necessarily all referringto the same embodiment. Furthermore, the particular features,structures, or characteristics may be combined in any suitable manner inone or more embodiments. Thus, the particular features, structures, orcharacteristics illustrated or described in connection with oneembodiment may be combined, in whole or in part, with the featuresstructures, or characteristics of one or more other embodiments withoutlimitation given that such combination is not illogical ornon-functional.

It will be appreciated that the terms “proximal” and “distal” may beused throughout the specification with reference to a clinicianmanipulating one end of an instrument used to treat a patient. The term“proximal” refers to the portion of the instrument closest to theclinician and the term “distal” refers to the portion located furthestfrom the clinician. It will be further appreciated that for concisenessand clarity, spatial terms such as “vertical,” “horizontal,” “up,” and“down” may be used herein with respect to the illustrated embodiments.However, surgical instruments may be used in many orientations andpositions, and these terms are not intended to be limiting and absolute.

Any patent, publication, or other disclosure material, in whole or inpart, that is said to be incorporated by reference herein isincorporated herein only to the extent that the incorporated materialsdoes not conflict with existing definitions, statements, or otherdisclosure material set forth in this disclosure. As such, and to theextent necessary, the disclosure as explicitly set forth hereinsupersedes any conflicting material incorporated herein by reference.Any material, or portion thereof, that is said to be incorporated byreference herein, but which conflicts with existing definitions,statements, or other disclosure material set forth herein will only beincorporated to the extent that no conflict arises between thatincorporated material and the existing disclosure material.

What is claimed is:
 1. A catheter comprising: a catheter shaft having aproximal end portion and a distal end portion, the catheter shaftdefining a fluid delivery lumen and an inflating lumen; a balloonconfigured to be coupled to the distal end portion of the cathetershaft, wherein the balloon defines a volume in fluid communication withthe fluid delivery lumen and flow-coupled in-situ with the inflatinglumen, wherein the balloon and the inflating lumen are partiallypositioned within the fluid delivery lumen; and a plurality of energytransfer elements disposed on top of a flexible circuit and along atleast a portion of the balloon, wherein the plurality of energy transferelements and the flexible circuit are disposed on top of a metal spline,wherein the balloon and the metal spline are separately expandableand/or collapsible.
 2. The catheter of claim 1, wherein the plurality ofenergy transfer elements comprises at least one ablation electrode. 3.The catheter of claim 1, wherein the plurality of energy transferelements comprises at least one of a sensing electrode, a flexibleelectrode, a mapping electrode, and a pacing electrode.
 4. The catheterof claim 1, wherein the plurality of energy transfer elements aresituated along an outer circumference of the balloon when the balloon isin an expanded state.
 5. The catheter of claim 1, wherein the metalspline is configured to support the balloon and to be coupled to thedistal end portion of the catheter shaft, wherein the metal splinecomprises a plurality of individual splines.
 6. The catheter of claim 5,wherein each spline is configured to support at least one of theplurality of energy transfer elements.
 7. The catheter of claim 5,wherein each spline is configured to support at least one temperaturesensor.
 8. The catheter of claim 5, wherein each spline is configured tosupport the flexible circuit including at least one of the plurality ofenergy transfer elements and a temperature sensor, and wherein theballoon is configured to compress the flexible circuit toward a tissue.9. The catheter of claim 8, wherein the temperature sensor is configuredto detect a temperature at an interface between the balloon and thetissue.
 10. The catheter of claim 8, wherein the flexible circuit isconfigured to overhang edges of the metal spline.
 11. The catheter ofclaim 10, further comprising a bridging flexible portion configured toconnect two overhanging flexible circuits.
 12. The catheter of claim 1,wherein the balloon comprises at least one internal electrode.
 13. Thecatheter of claim 1, wherein the balloon is a double balloon configuredwith an inner balloon and an outer balloon.
 14. The catheter of claim 1,further comprising an over-coating disposed only in a non-ablationregion of the plurality of energy transfer elements.
 15. An ablationcatheter assembly comprising: a catheter shaft defining a fluid deliverylumen and an inflating lumen; a balloon attached to the catheter shaftand the fluid delivery lumen, wherein the balloon is transformablebetween a delivery state and an expanded state, and wherein the balloon,in the expanded state, spans an area greater than a cross sectional areaof the catheter shaft to which the balloon is attached, wherein theballoon and inflating lumen are partially positioned within the fluiddelivery lumen; and a plurality of ablation electrodes positioned on topof a flexible circuit and along an outer surface of the balloon when theballoon is in the expanded state, wherein the plurality of ablationelectrodes and the flexible circuit are positioned on top of a metalspline, wherein the balloon and the metal spline are separatelyexpandable and/or collapsible.
 16. The assembly of claim 15, furthercomprising at least one sensing electrode positioned along the outersurface of the balloon, when the balloon is in the expanded state. 17.The assembly of claim 15, wherein the metal spline is configured tosupport the balloon and to be coupled to a distal end portion of thecatheter shaft, wherein the metal spline comprises a plurality ofindividual splines.
 18. The assembly of claim 17, wherein each spline isconfigured to support at least one of the plurality of ablationelectrodes.
 19. The assembly of claim 17, wherein each spline isconfigured to support at least one temperature sensor.
 20. The assemblyof claim 17, wherein each spline is configured to support the flexiblecircuit including at least one of the plurality of ablation electrodesand a temperature sensor, and wherein the balloon is configured tocompress the flexible circuit toward a tissue.
 21. The assembly of claim20, wherein the temperature sensor is configured to detect a temperatureat an interface between the balloon and the tissue.
 22. The assembly ofclaim 20, wherein the flexible circuit is configured to overhang edgesof the metal spline.
 23. The assembly of claim 22, further comprising abridging flexible portion configured to connect two overhanging flexiblecircuits.
 24. The assembly of claim 15, wherein the balloon is a doubleballoon configured with an inner balloon and an outer balloon.
 25. Theassembly of claim 15, further comprising an over-coating disposed onlyin a non-ablation region of the plurality of ablation electrodes.